The present invention relates to a compensation device for vibrations of an angle variable in a printing material processing machine, having an associated actuator which affects the angle variable, the compensation device being supplied with a signal which is representative of the angle variable characteristic and the compensation device generating an output signal for the actuator.
Periodic noninteger orders of vibration in comparison with the machine frequency in an angle variable, an angle of rotation, or an angle signal of a cylinder in a printing material processing machine, in particular a sheet or web processing printing press, have a negative effect on the precision of successive printed objects on a printing material. These negative effects may result in printing problems, in particular so-called doubling. Such negative effects may become relevant in particular between mechanically isolated parts of a printing material processing machine, in particular two or more groups of printing units of a sheet processing printing press. The vibrations result in fluctuations in the angle of rotation differences at the circumferences of a first cylinder and a second cylinder, resulting in a corresponding change in the circumferential register to the sheet transfer angle directly at the transfer of sheets between the separately involved printing units.
For a printing press driven by individual electric motors, a regulating means using control circuits for each electric motor is disclosed in German Patent Application No.197 40 153 A1, for example, for compensating periodic vibrations. In this periodic compensation regulator, a torque setpoint which is sent to a final control element receives an additional torque which is determined by a compensation regulator which processes the setpoint-actual value difference or the difference is determined from the torque setpoint and the actual value of the angular velocity or the angle of rotation. In this procedure, a dynamic process model is necessary to ensure stability. This form of regulating the system is also associated with a high computational complexity. Furthermore, the sampling time must be selected to be so long that a multiple of the period of the vibrations to be compensated may be included, but this is problematic in the case of variable printing press speeds.
In German Patent Application No. 100 53 237. 1, having a filing date of Oct. 26, 2000, a process of compensating mechanical vibrations, in particular rotational vibrations on a machine shaft, a cylinder, or a signal calculated from one or more coordinate values of one or more axes of rotation, in particular the difference between coordinates of two real machine shafts is disclosed. The rotational vibrations are represented spectrally in discrete frequency components, and each component is compensated by an essentially harmonic moment of the same frequency and a certain amplitude and phase in that the harmonic moment is impressed directly on the machine shaft or indirectly via an actuator. The process in question requires knowledge of the reinforcements and phase shifts of the underlying process for the frequencies to be compensated in order to be able to introduce harmonic moments of appropriate intensities and phases.